Saturday, February 13, 2010

Jeanne Marie Acceturo is our guest writer who has ALL the answers for you:

One hundred fourteen wood-warbler species nest in the Americas and Bahama Islands. But only two of them use cavities for nesting: the Prothonotary Warbler (Protonotaria citrea) (PRWA, bottom photo) and Lucy's Warbler (Vermivora luciae) (LUWA, top photo).

Newly returning males of both species will soon arrive after migrating. They’ll define and defend territories before females arrive a week or two later (in April for the bulk of most breeding sites in the United States).

Males do all the wooing. Females make all the choices. Her big decisions: Which male has excellent taste in real estate? What constitutes a million dollar listing in the wood-warbler world?

Unlike PRWA and LUWA, other wood-warbler species prefer nesting sites within dense shrubs, atop a tree branch, or in a nook under a tangle of ground cover. Our two cavity nesting wood-warblers prefer otherwise, instead often utilizing dead snags or live trees where standing water provides a moat directly below the nest site.

Last year’s Downy Woodpecker hole? To a PRWA, it’s the perfect choice. Bald cypress, willow and sweet gum are the typical host trees. Male PRWAs make a platform of moss inside each suitable cavity in their territory. The females construct the nest and include mosses and liverworts.

Why? Perhaps it’s because damp nesting material increases humidity inside the cavity so that eggs are less likely to dry out.

But that still doesn’t explain why PRWAs use cavities. The mystery remains. One theory relates to the added protection obtained from living inside a limb hidden from predators such as marauding rat snakes.

In an all-too-familiar story, however, much of their preferred bottomland hardwood forest is disappearing. People have destroyed 90 percent of this habitat for logging, agriculture and other development. Fortunately, there’s good news: PRWAs sometimes use nest boxes when they’re erected in suitable locations.

Lucy's Warbler, the West Coast first cousin of the more East Coast based PRWA, also nests near water. But where’s a LUWA likely to find water within the lower Sonoran desert habitat that it favors? Not too many places. So LUWA changes its game plan: old Gila Woodpecker holes or abandoned Verdin nests sometimes become Home Sweet Home. So do crevices behind loose tree bark, natural cavities, or, less commonly, spaces among large networks of loosely tangled roots in riverbanks.

Populations of LUWAs have dropped for an obvious reason: the Southwest has been developed intensely. Unfortunately, LUWA rejects nest boxes, but where LUWA’s natural habitat of mesquite forest has been lost to logging and water diversion, introduced (and invasive) tamarisk trees pinch hit as substitute nesting sites.

Are either PRWA or LUWA listed as threatened or endangered? Not yet, but conservation of these two species’ remaining populations presents a cautionarytale — one that depends on habitat conservation as a rule and not an option.

That’s because during the “winter,” it’s possible to see both the subspecies that occur within the Palm Warbler species.

More details follow:

Telling both subspecies apart in the winter/non-breeding season may and can be challenging. Underline the last sentence (!)

To wit: Although you can see both subspecies during the non-breeding season/winter in Florida, the pale “Western” subspecies (Dendroica palmarum palmarum) often adds a touch more of yellow under its belly during the fall (through winter).For this reason, some population members of “Western” may look like the “Yellow” (East Coast” subspecies, D. p. chrysolepis. The latter (the “Yellow” East Coast version) is much brighter during the breeding season than the “Western” Palm Warbler subspecies.

Got all that?

If not, here's a MAJOR tip.....

It’s an excellent field mark that helps you tell the two subspecies apart:the yellow eye-ring that’s shown in the “Yellow” Palm Warbler (D. p. chrysolepis).In contrast, the “Western” Palm has a WHITE eye-ring.

Even more details about the two subspecies yellow color follows:“Western” yellow has a contrasting pattern where the yellow ends and the rump is a duller green (but more yellow in the “Yellow” East Coast subspecies (D. p. chrysolepis).

Note there are intergrades and, indeed, a potential breeding area in Canada where both subspecies may successfully mate with each other and have viable offspring.

Despite all the details I’ve already present, this account oversimplifies how to identify both subspecies from one another. Excellent drawings of both subspecies appear in “A Field Guide to the Warblers of North America” (Jon Dunn and Kimball Garrett) (plate #20, page 82). More details about how to tell them apart are described on p. 366 in this book.

The plates are “Must See” viewing for warbler fans like you, Mr. King, but I hope the account above answers your question.

Monday, February 1, 2010

Now look at the above graphic that shows the annual population changes of Kirtland's Warbler in Michigan during the last 20 years.

Hmmmm.......Do you think the current majority of folks who answered the quiz are correct? Incorrect?

Truth be told, the Michigan DNR's habitat management plan is a huge victory for the federally endangered Kirtland's.Their populations in 12 central-northcentral Michigan counties continue to thrive. Prescribed fires have helped create optimum conditions in their Jack Pine community whereby managers have helped Kirtland's rebound from the brink of extinction in the late 1980s.

Of course, Wisconsin breeding populations of Kirtland's are also big news. During the past three breeding seasons, Wisconsin has hosted newborns in at least two counties. For more details about the discovery of Kirtland's Warbler in Wisconsin and an overview of their breeding abundance, see one or more of my June and July, 2009 updates/articles in the archives section of this wood-warbler blog.

By the first week of March, which returning wood-warbler is the second or third most abundant wood-warbler species in the USA?

Can you identify the correct order (top to bottom) of wood-warblers in the five photos on the left from the 11/10/10 posting?

In how many states does Kirtland's Warbler regularly nest?

With a clutch of six or seven eggs, this wood-warbler lays the largest clutch:

Which are three of the earliest dispersing/migrating wood-warblers?

How many New World wood-warbler species exist?

Can you identify the correct order (top to bottom) of wood-warblers in the five photos on the left from the 3/2/10 posting?

Which wood-warbler is typically the earliest long-traveling migrant back on the East Coast? West Coast?

Which wood-warbler species has gained the most population by percentage in the last 20 years?

FAB FIVE QUIZ: From top to bottom, can you correctly ID the species in order from the following choices?

Approximately how many miles are trans-oceanic migrating Blackpoll (Warbler) traveling if they begin in New England and arrive in northern S. America (For help, see the 9/29/09 article)?

Pretend you're attending an upcoming Christmas Bird Count (CBC) in any of the lower 48 states. Which two wood-warbler species are the most likely ones MOST people would see?

Can you name two wood-warbler species that are breeding endemics to one USA state?

Beyond it now being the most likely viewed wood-warbler from the Upper Midwest to the upper Eastern Seaboard/upper New England area, the Yellow-Rumped Warbler holds the following distinction from most other USA wood-warblers (& other songbirds):

In terms of sheer numbers, which wood-warbler is the most common on our beautiful, amazing, avian-filled planet?

How many wood-warblers in North America look similar year-round because they don’t undergo a prealternate molt?

Given the "Dendroica" genus hosts the greatest number of North American wood-warbler species, which member of this genus is the largest in the continental USA?

Can you name the two hybrid forms that sometimes result when Golden-Winged and Blue-Winged Warbler mate?

On the West Coast, which wood-warbler is one of the earliest dispersing species after nesting?

Among the species listed in the 5/29/09 article (on the left), which one is considered extinct?

Common Yellowthroat was often previously named differently in many field guides as XXXXXX Yellowthroat?

Which common wood-warbler's breeding range is split into an eastern and western subspecies breeding population?

Which sequence of weather conditions typically result in a "fallout" of wood-warblers during the spring on the Gulf Coast?

Yellow-Breasted Chat

If it's not a wood-warbler, then into which taxonomic placement has Yellow-breasted Chat previously been proposed?

Which "New World" wood-warbler species has the most extensive breeding area?

Unlike Blackpoll that undertake a long migration (see 1/8/09 article), which wood-warbler has populations that do NOT migrate?

What behavior displayed by American Redstart is different than most other songbird order members?

Which wood-warbler species spends the winter in large numbers in higher latitudes than any other wood-warbler?

(Audubon's) Yellow-Rumped Warbler

. . . is one of the four subspecies of Audubon's Yellow-Rumped Warbler, while another two are considered "Myrtle's" Yellow-Rumped Warbler. According to Jon Dunn and Kimball Garrett's "Warbler" field guide, subtle variations in the pitch (frequency level) of the call notes help distinguish an Audubon's vs. a Myrtle's subspecies (in addition, of course, to assessing their different field marks).

Is the song or call of the Yellow-Rumped Warbler subspecies (Myrtle and Audubon's) the best way to tell them apart?

Warbler Guy, do you provide us the answers to your quizzes (scroll down the page to see each new one)?

Given most songbirds hop on the ground, how many wood-warblers possess as an important field behavior the ability to walk?

Which wood-warbler species are some the most improbable and/or rare to see on the West Coast? (Answer at end of related article on left.)

Common Yellowthroat (Geothlypis trichas)

Next to the Yellow-Rumped Warbler, Common Yellowthroat is the next most likely non-breeding season wood-warbler to overwinter in extreme, northern latitude states, especially if a micro-habitat or mild winter exists.

True or False: More wood-warbler (Parulidae family) species nest in the USA & Canada than in the tropics?

Hermit Warbler (Dendroica occidentalis)

Like many resident tropical wood-warbler family members, the Hermit Warbler displays little seasonal change in plumage. Interestingly, young and adult birds in low elevation sites leave breeding territories before the start of prebasic molt (after the breeding season) and presumably move to higher elevations to molt.

Kirtland's Warbler (Dendroica kirtlandii)

Like all Dendroica genus members, the Kirtland's Warbler displays a characteristic feeding behavior that is termed "hover and glean" as it searches for insects during the breeding season.

In my opinion, the most challenging autumn/basic plumage wood-warbler to ID is:

Which is the single wood-warbler species that nests in the USA, but is not in the Parulidae family like all the other 51 other regularly-occurring wood-warbler species existing north of Mexico in North America?